Because макаро́ни refers to any kind of pasta (except perhaps noodles, that would be ло́кшина), not just to macaroni.

The English Wikipedia has this picture in the article 'macaroni':

This would be called «макарони-ріжки» (literally 'horn pasta') or just «ріжки» ('horns').

The Italian Wikipedia has this picture in the article 'Maccheroni':

I'd call this «макаро́ни-тру́бочки» (literally 'pipe pasta').

Although for purposes of food labels in the United States at least, ‘macaroni’ means any egg-free pasta. (Look for ‘enriched macaroni product’ on the labels.)